This section provides background information related to the present disclosure which is not necessarily prior art.
Hermetically sealed motor-compressor units are prevalent in refrigeration applications where the motor-compressor units are employed to compress refrigerant vapor. The compressor is generally driven by an electric motor which rotates a crankshaft of the compressor at relatively high speeds. These hermetically sealed motor-compressor units are frequently located in environments where it becomes necessary to protect the connections to the electrical system and ensure that the integrity of the electrical connections is maintained. Typical electrical connections for a hermetically sealed compressor include power lines for providing electricity for operating the electric motor and control circuitry which monitors the operation of the compressor.
Typically, one or more hermetic terminals are provided in the motor-compressor unit to allow electric power and/or electrical monitoring systems to extend through a housing of the motor-compressor unit. Power supply terminals typically include a body member welded or otherwise secured to the housing. The body member has a plurality of current conducting pins which are hermetically secured to and extend through the housing such that one end of each current conducting pin is located within the housing and the opposite end is located outside the housing. Electrical insulating and sealing material such as glass and/or epoxy forms a hermetic seal between each current conducting pin and the body member. The internal end of each current conducting pin is connected to electrical leads of the electric motor. The external end of each conductor is connected to a power supply by way of a connector block that attaches to the current conducting pins of the terminal. Typically, the electric motor is powered by a 3-wire single-phase electricity distribution system and the terminals include three current conducting pins.
In order to provide protection and sealing for the terminals, a terminal box is attached to the housing around the various terminals. The terminal box includes the appropriate cutouts to provide access to the various terminals, and seals are provided around these cutouts in order to protect the terminals from the outside environment. Typically, an external connector block is positioned over the power supply terminal with this external connector block being held in place by a terminal box cover which closes the terminal box. The external power is typically provided by a plurality of conductors which are attached to the external connector block. Each of the plurality of conductors electrically engages a respective current conducting pin when the external connector block is assembled to the power supply terminal. Once this connection is made, the terminal cover is attached to the terminal box to retain the external connector block and isolate the electrical connections within the terminal box.
On the inside of the housing, an internal connector block is positioned over the power supply terminal. The internal connector block routes electrical power from the power supply terminal to the electric motor which drives the compressor. The internal connector block includes a plurality of connectors or end fittings which frictionally engage the current conducting pins of the power supply terminal. It is preferred that the size of the internal connector block be kept as small as possible so that it does not interfere with the other components of the motor-compressor unit located inside the housing.
More frequently, new compressor applications require ever increasing electrical amperages (i.e., a higher electrical current) to be supplied to the electric motor. In some cases, requested power ratings for new applications exceed that of the largest available standard power supply terminal. One approach to dealing with higher amperage is to increase the diameter of the current conducting pins, which in turn increases the size of the power supply terminal, the external connector block, and the internal connector block.
In addition to creating unwanted size increases, such a solution requires investments in tooling and other disadvantages.